1. Field of the Invention
The present invention relates to a method and apparatus for processing data, wherein a data track of an optical recording medium is scanned with a light beam to perform at least one of data recording on the medium and data reproduction from the medium.
2. Related Background Art
Various types of recording media such as disk-like recording media, card-like recording media, and tape-like recording media are known as conventional data recording media for recording data and reading out the recorded data using light. These optical data recording media are classified into read/write media and "read-only" media. Data is recorded on a recordable medium by scanning a data track with a light beam modulated with recording data and focused into a small beam spot. Data is recorded as an optically detectable data pit array.
Data is reproduced from a recording medium as follows. A data pit array of a data track is scanned with a light beam spot having a power which does not allow recording of the recording medium, and a beam reflected by or transmitted through the recording medium is detected to perform data reproduction. A so-called optical head is used to radiate the light beam spot onto the recording medium and to detect the beam reflected by or transmitted through the recording medium. The optical head can be moved relative to the recording medium along the direction in which the data tracks of the recording medium extend and a direction perpendicular to the direction in which the data tracks extend. This relative movement allows scanning of the data track with the light beam spot. Of all the optical data recording media, a card-like optical data recording medium (i.e., an optical card) is the most promising medium as a data recording medium having a relatively large capacity due to its compactness and portability.
FIG. 1 is a schematic plan view of a WORM (write one read many type) optical card, and FIG. 2 is an enlarged view of a track portion of the optical card.
Referring to FIG. 1, a large number of data tracks Ta extending along an LF direction are formed on a data recording surface of an optical card C. These data tracks are illustrated in an enlarged manner by the alternate long and two short dashed lines in FIG. 2. A home position HP is defined on the data recording surface of the optical card C and serves as a reference position of access to the data tracks Ta. The data tracks Ta are arranged in an order of Ta1, Ta2, Ta3, . . . from the side close to the home position HP. These data tracks consist of two types of tracks, i.e., tracks recorded with data and tracks not recorded with data. Data is recorded in each recorded track in the form of recording pits P. As shown in FIG. 2, tracking tracks Tb and the data tracks Ta are alternately formed on the data recording surface. Each tracking track Tb is used as a guide for auto-tracking (AT) so as to keep a light beam spot on a predetermined data track during scanning using the light beam spot in the data recording/reproduction mode.
In a conventional apparatus, however, the following drawback is presented during a track jump. Assume that a light beam spot is to cross the tracks shown in FIG. 2. When the light beam spot crosses a recording pit of a recorded track, a tracking error signal is undesirably generated. In this case, although the light beam spot has not reached a target track, the jump operation is interrupted halfway, and the operation mode is switched to a tracking servo mode. For this reason, an operation error occurs due to an influence of data already recorded on the conventional medium, and an accurate jump operation may not often be performed.